Re: Frequency Valve

[quk@isham-research.demon.co.uk (Phil Payne)]

In message <199809161820.OAA01803@urq.East.Sun.COM> Robert Houk - WorkGroup Server Firmware writes:

> Ummm . . . not quite. The FV acts to bleed down the fuel system pressure
> (the active fuel system pressure driving the injectors, not any of the
> dozen other "fuel system pressures" you can measure). I think (it's been
> awhile) that it, in conjunction with the CPR (Control Pressure Regulator)
> act to control backpressure on the fuel distributor valve assembly, thus
> controlling the fuel pressure feed to the injectors.

The explantion _I_ heard is that the FV acts to reduce pressure within
the metering head below the diaphragm, thus causing the diaphragm to
bow out slightly below the take-off points for the injector lines.

Supposedly this is a mechanism to improve flow without affecting
pressure.  Not quite how I understood hydrodynamics to work, but still ..

> You should be able to hear the little critter buzzing happily to it-
> self at idle. If it is not, check to see if it is being driven by the
> ECU. There is ("should" aka "might" be) a two-conductor socket dangling
> by the ignition coil ('83 UrQ; dunno 'bout any other car...) which is
> a test tap to monitor the FV signal ...

The reason for the test socket is that the line from the ECU to the
frequency valve is resistive.  Scott Mockry investigated my failure
to get a decent duty cycle reading off the valve itself, and found (it's
in the diagrams, so I should have found it first) that the line is about
8 ohms.  The test socket is connected directly to the ECU pin.

--
 Phil Payne
 Phone: 0385 302803   Fax: 01536 723021
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